Semiconductors are the basis of all modern electronics—from the smallest switches in the widely prevalent personal computers and smartphones to large-area displays in various information media. The conducting properties (e.g. currents passing more easily in one direction than the other, variable resistance, etc.) of these materials are made truly useful because they may be purposely altered through doping, which is the deliberate and controlled introduction of impurity atoms into the crystal structure.

Through recent advancements in the field, two-dimensional semiconductors (natural semiconductors with thicknesses on the atomic scale) and complex electronics based on them have tantalized potentials for myriad applications such as nano-circuitry and flexible electronics, but the efficient assembly of complex 2D devices on integrated circuits requires novel scalable procedures not yet realized. Now, collaborative research led by POSTECH has successfully developed a process to directly write integrated circuits on a 2D semiconductor using visible laser.

Professor Moon-Ho Jo, from the Department of Materials Science and Engineering, fabricated integrated circuits (ICs) on a 2D semiconductor (2H-MoTe2) using a self-aligned doping approach with a scanning visible light probe. The research team demonstrated that this elegant approach of programmable doping is not only accurate and reliable but also efficient. This achievement was published in Nature Electronics as an editorial selection for the celebration of the 60 years of the ICs.

The team used chemical vapor deposition and mechanical exfoliation methods to deposit metal patterns onto 2H-MoTe2 semiconductor layers and created otherwise pristine (nominally undoped) n-type semiconductors. At this point, laser was selectively scanned over the metal patterns. The team discovered that the MoTe2 channels between the illuminated contacts displayed p-type semiconductor characteristics. In other words, the team developed a reliable, controllable and efficient method of p-type doping for 2D semiconductors.

Professor Jo expressed his anticipation in applying this new approach to the development of massively parallel circuitry based on 2D semiconductors as this method allows for accurate and quick writing of 2D circuits with both n-type and p-type characteristics on the same atomic plane.

This work was supported in part by the Institute for Basic Science (IBS) and the National Research Foundation of Korea.